Photochemical preparation of polyphenylalkanes



Patented June 5, 1951 PHOTOCHEMICAL PREPARATION OF POLYPHENYLALKANES Ralph B. Thompson, Riverside, Ill., assignor to Universal Oil Products Company, Chicago, 111., a corporation of Delaware No Drawing. Application January 31, 1948, Serial No. 5,688

8 Claims. 1 This invention relates to a process for conrdensing a hydrocarboncontainingan alkyl group to Lform .a hydrocarbon of higher molecular Weight. More particularly, the process relates to .thecondensation of an alkyl aromatic hydrocarbon 2130 form .an aromatic hydrocarbon of higher molecular-weight.

:An object of this invention is to condense a Fhydrocarboncontaining an alkyl group to form a hydrocarbon of *higher molecular weight.

Another object of this invention is to condense .an alkyl" aromatic hydrocarbon in the presence of an alky1;ketone to form a hydrocarbon of higher molecular weight.

A furtherobject of this invention is to condense an alkyl benzene hydrocarbon to form a diphenyl alkane hydrocarbon.

.One specific embodiment of this invention relates to a process for producing a hydrocarbon of higher molecular weight which comprises reacting a hydrocarbon having an alkyl group in the; presence of a low molecular weight .allryl ketone and under the influence of ultraviolet light.

7 Another embodiment of this invention relates to a process for producing a polyarylalkane which comprises condensing an arylalkane in the presence of a low molecular weight alkyl ketone and under the influence of ultraviolet light.

- 'A'further-embodimentof this invention relates to a process for producing a polyphenylalkane which comprises condensing a phenylalkane having an alkyl group represented by the formula wherein R and R represent at least one member of the group consisting of hydrogen and an alkyl group in the presence of a low molecular weight alkyl ketone and under the infiuenceor" ultraviolet light.

Hydrocarbons which are condensed by my process to form hydrocarbons of higher molecular weights include parafiins, olefins, haphthenes, and aromatics "each containing 'an alkyl group which hydrocarbons react in the presence of an alkyl ketone to split out hydrogen and effect a condensation of two fragments resulting from the loss of hydrogen from the hydrocarbon being treated.

Aromatic hydrocarbons particularly suitable for use in my process have an alkyl group in which a hydrogen atom is combined with 'a' carbon atom adjacent to the aromatic ring. i Such hydrocarbons may be represented by .thegeneral .formula':

wherein Ar represents an aromatic group and .R and R represent at least one member of the group consisting of .a hydrogen atom and an alkylgroup. Benzene hydrocarbons particularly suitable .for my process .comprise toluene, ethylbenzene, isopropylbenzene, and other a1kylben zene hydrocarbons of higher molecular Weights.

The above indicated hydrocarbons containing alkyl groups particularly the .alkylbenjzene hydrocarbons, are reacted singly or in admixture with one another in the presence of an alkyl ketone, particularly a low molecular weight alkyl ketone as acetone, methylethylketone, diethylketone, methylisopropylketone, ethyl ,propylketone, methylbutylketone, and the likeyunder the influence of light containing ultraviolet radiation to form higher boiling hydrocarbon condensation products generally derived by, the combination of two molecular proportions of the hydrocarbon and a splitting out of one molecular proportion of hydrogen. The process is carried out in batch or continuous types of operation for a time sufficient to form condensation products from a portion of the hydrocarbons, particularly from a portion of the alkyl aromatic hydrocarbons undergoing treatment.

The formation of aromatic hydrocarbongjcondensation products takes place slowly when a mixture of an alkylbenzene and an alkyl k'etone is exposed to sunlight or other light containing ultraviolet radiation at a temperature of from about 0 to about C. but preferably at a temperature of from about 20 to about 40 C.

during a relatively long period of time. After the reaction has been carried out, the reaction mixture is subjected to a suitable separation method such as fractional distillation to remove the unconverted alkyl hydrocarbon and to recover the higher-boiling hydrocarbon condensation product such as polyarylalkane. The excess of unconverted hydrocarbon is suitable for recycling to the process.

Although the mechanism of the condensation reaction of this process is not known completely, it seems probable that the reaction proceeds through the formation of free radicals produced during the decomposition of the alkyl ketone under the influence of light. Although these concepts should not be misconstrued to limit the broad scope of the invention, it appears that when under the influence of ultraviolet light, an alkyl ketone decomposes to form free alkyl radicals and that these free alkyl radicals react with a the hydrocarbon such as ethylbenzene as illustrated in the following equations showing the condensation of ethylbenzene in the presence of methyl radicals derived from acetone or another methyl ketone.

The following example is given to indicate results obtained in this process but these data should not be misconstrued to limit the broad scope of the invention.

A mixture of 95% by volume of ethylbenzene and by volume of acetone was placedin a colorless glass bottle, the bottle was tightly corked, and was then exposed outdoors to spring and summer sunlight during a period of four months, at a temperature of from about to about C. The resultant hydrocarbon mixture was then distilled to remove excess ethylbenzene and acetone from a residue which crystallized on cooling. The residue which represented 6% by weight of the original ethylbenzene was recrystallized frompetroleum ether and then identified as 2,3-diphenylbutane. Also some oily material was obtained consisting of the liquid stereoisomer of 2,3-diphenylbutane.

Another example of the process is the condensation of cumene in the presence of acetone at a temperature of from about 0 to about C. and under the influence of ultraviolet light, whereby to produce 2,3-dimethyl-2,3-diphenylbutane.

I claim as my invention:

1. A process for producing a polyphenylalkane which comprises condensing in the presence of an alkyl ketone and under the influence of ultraviolet light a, phenylalkane consisting of phenyl and alkyl groups and having a hydrogen atom attached to a carbon atom adjacent to the benzene ring.

2. The process of claim 1 further characterized in that said phenylalkane is ethylbenzene.

3. The process of claim 1 further characterized in that said phenylalkane is cumene.

4. The process of claim 1 further characterized in that said alkyl ketone is acetone.

5. A process for producing 2,3 dimethyl- 2,3-diphenylbutane which comprises condensing cumene in the presence of an alkyl ketone at-a temperature of from about 0 to about 100 C. and under the influence of ultraviolet light.

6. The process defined in claim 5 further characterized in that said alkyl ketone is acetone.

7. A process for producing 2,3-diphenylbutane which comprises condensing ethylhenzene in the presence of an alkyl ketone at a temperature of from about 0 to about 100 C. and under the influence of ultraviolet light.

8. The process of claim '7 further characterized in that said alkyl ketone is acetone.

RALPH B. THOMPSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS I OTHER REFERENCES Ellis et a1., Chemical Action of Ultraviolet Rays (1941), pp. 421, 425-431. 

1. A PROCESS FOR PRODUCING A POLYPHENYLALKANE WHICH COMPRISES CONDENSING IN THE PRESENCE OF AN ALKYL KETONE AND UNDER THE INFLUENCE OF ULTRAVIOLET LIGHT A PHENYLALKANE CONSISTING OF PHENYL AND ALKYL GROUPS AND HAVING A HYDROGEN ATOM ATTACHED TO A CARBON ATOM ADJACENT TO THE BENZENE RING. 